I think I may have one of these. I didn't give it much attention because it uses the relatively hard to get 4027 4k x 1 chip and uses multiple voltages. However, looking at the data sheet, it should be possible to substitute more common 4116 chips without any change to the voltage supplies, just strapping the CS pin high or low; or even use 4164 chips, which are even more common, require only +5, and are cheaper, but would require additional (but simple) modifications to the power rails.

Maybe it's worth revisiting the board, possibly even scanning one, to have a genuine period-correct RAM option that can fit 48K in a single board.